Neither 12, nor 13 is printed, while these numbers were in fact returned. I understand what you are saying, and it is clear that something that returns None is not printed. But if the function does return something, this still doesn't guarantee that the result is printed. It depends on the context.

OK, then it is probably a question of what is "invoking" the REPL in the first place. pyboard does not, but any serial terminal does. I see that this issue is probably not related to the board as such, but to the software on the computer.